The present invention relates to a process for qualitative and/or quantitative analysis of an analyte, in particular, an analyte in a biological solution. The present invention concerns, as well, a sensor, which is especially operable for transforming the process.
The purpose of such biosensors is the specific detection of biomolecules. There are a multitude of scientifically and economically important fields in which biosensors can be deployed for this purpose. In this regard, for example, the medical diagnostic field, the environmental diagnostic field, the development of pharmaceutical materials or the monitoring of industrial biotechnology processes come to mind. Particularly noteworthy examples of the scientific and economic significance of biosensors are the GeneChip® offered by Affymetrix® and the therewith deployed products, which find ever-increasing use in academic and industrial research.
The requirements imposed on such biosensors are consequently multi-fold. It is typically desired that such biosensors have a high sensitivity and specificity with respect to small analyte amounts and a high measurement throughput, a high robustness and, frequently, the possibility, as well, for miniaturization and for integration thereof into arrays. Moreover, it is advantageous if the biomolecules to be detected do not need to be marked with fluorophors or with radioactive isotopes, as is conventional.
A widely used, economically successful, type of sensor is based on the effect of Surface Plasmon Resonance (SPR). In this connection, a multitude of measurements can be performed up to and including the characterization of the bonding kinetics of biomolecules. Typically, the protein amounts can be measured down to quantities in the pM range.
Proteins, which only occur in small concentrations, can, therefore, not be detected by these approaches. A variation of the SPR process, which is substantially more sensitive than the above-noted approaches, exploits the fluorescence of the analyte. The disadvantage of this variation is the necessity to mark the analyte with fluorophor.
Fluorophor markings are also necessary in connection with the above-noted GeneChip®, a widely used process with a relatively high integration grade. This process permits an entire genome to be arranged in an array. The sensitivity of this process is increased by amplification of the nucleic acid analytes via the polymerase chain reaction (PCR). The process is consequently very sensitive. In this form, however, the process is limited to the nucleic acids as the analytes. In connection with the use of electro-chemical sensors, further material must typically be added to the actual analyte. The reactions of the added further material leads to the release, as a function of the concentration of the actual molecule of interest in the analyte, of electrical charge carriers, which are detected as current. In another configuration, there is additionally detected, via the use of the capacitative measurement process, the di-electric property changes of the measurement system, or impedance spectroscopy is deployed.
A further widely used sensor type is the quartz micro balance or scale, which has the important advantage of a compact construction in comparison to the SPR systems. The Surface Acoustic Wave (SAW) micro balance or scale is comparable in its sensitivity with the SPR sensors and the SAW micro balance or scale is most commonly deployed for measurements in the gas phase. In the liquid phase, which is more relevant for many inquiries of interest, detection via the SAW sensors suffers due to the strong damping exerted by the liquid.
Mass spectrometry processes, such as Surface Enhanced Desorption/Ionization (SELDI), can, in fact, be performed without markings on the analytes and the sensitivity of such processes is sufficient under favorable conditions for measurements into the attomol range. On the other hand, the hardware effort is comparatively high, the heretofore possible integration grade is still low, and a quantification of the analyte is difficult.
In connection with the conventional state of the art, several biosensor types are known. In practice, it has, however, heretofore not been possible to develop a biosensor which simultaneously and substantially satisfies all of the above-noted analyte measurement requirements.